Известия Томского политехнического университета: Инжиниринг георесурсов (Aug 2017)
Complexes of Bryozoa and Rugose corals of Emsian Stage of western Altai-Sayan folded area
Abstract
The relevance of the research is justified by the need to clarify the evolution of Bryozoa and Rugose corals in the Emsian Age due to the changes in the stratigraphic scheme of Salair. The aim of the work is to analyze the change of Bryozoa and Rugose corals complexes of the western part of the Altai-Sayan Folded Area during Emsian Age to identify the boundaries of their rejuvenation. The methods used in the study. Bryozoa and Rugose corals have been studied in thin oriented sections under a binocular microscope according to conventional methods. In determining the delimitation of species the methods of mathematical statistics were used. The results. Clarifying and improving the stratigraphic scheme of Emsian Stage of Salair Devonian due to the appearance of new data on conodonts caused the need to analyze the evolution of the other groups of fauna. The authors have carried out the comparative analysis of the spread of Bryozoa and Rugose corals complexes, and boundaries of their rejuvenation within the Emsian Stage of the western part of the Altai-Sayan Folded Area. Itwas found out that the complex of Emsian Bryozoa and Rugose corals clearly differs from Pragian Stage and from the Eifelian Stage. The Bryozoa complex consists of three clearly distinguished associations that characterize the Lower and Middle Salairka, Upper Salairka - Middle Shanda and Upper Shanda section intervals of the Emsian Stage. Bryozoa of Lower Salairka association have spacious time at Middle Salairka time, forming a single association which characterizes the Lower and Middle Salairka biozone. Thus, the assignment of Lower Salairka Bed to Pragian Stage is not justified. The Bryozoa association of «Belovo» Horizon does not differ from both Higher Salairka and Lower-Middle Shanda. On Rugose corals «Belovo» Horizon is traced distinctly unlike Salair on the territory of Gorny Altai. Rugose corals spacious time coincides with the Higher Salairka and Lower-Middle Shanda period. The Upper Shanda Bed of Rugose corals differs from the Lower and Middle Shanda period, though it is on the level of the species diversity. Eifelian Rugose corals are characterized by a marked depletion of species in Salair and almost total absence in Gorny Altai. The boundary of rejuvenation of Pragian and Emsian complexes of Bryozoa and Rugose corals is the surface of discontinuity between Maliy Bachat Bed and Lower Salairka Bed. The rejuvenation of Emsian and Eifelian complexes is the surface of discontinuity between the Upper Shanda Bed and Maliy Salairka Bed.
